Project 1. Gene Expression During HSV-1 Latency and Reactivation Human neurotropic herpes viruses such as HSV cause much disease and suffering. The long-term objective of this project is to understand the mechanism of herpes simplex virus latency and reactivation at the molecular level. In this application, we propose to expand our study of the nucleosomal state of the viral DNA, as we believe that these structures play an important role in regulating viral gene expression. We will continue to examine the function of stable intron of the latency associated transcript (LAT) genes. Furthermore we will expand on our finding of differences in cell gene expression in latently infected and normal trigeminal ganglia. These goals will be achieved using the techniques of molecular virology and a mouse model of HSV infection. In the first specific aim, we will determine the distribution and role of the nucleosome in acute infection of mice. Further studies will relate these results to the situation during viral reactivation. In the second aim, we will continue our study of the functionality of the LAT gene. We will study the 2kb LAT intron, which is found in the nucleus of latently infected neurons yet in the cytoplasm of lytically infected cells. Our recent studies suggest that the intron plays a role in cellular stress response. We will determine jLAT intron function through studying its structure and the proteins associated with it. Our studies on the mechanism of the LAT antiapoptotic effect will be expanded in light of our recent progress. In the third specific aim, we will continue our study of the cell genes that are changed in expression in latently infected trigeminal ganglia. We wiil perform insitu hybridization to confirm the cell types that are altered in transcript levels, and immunohistochemistry to identify if the protein products are altered in amount jor distribution. An understanding of these changes will help- us recognize ways in which the latent virus alters the infected sensory neuron, presumably in order to maintain its latency. These studies will continue our investigation of herpes simplex virus latency and reactivation and further our understanding of the mechanism of latency in the peripheral nervous system.